Sliding member

ABSTRACT

A sliding member having a scuff resistant and abrasion resistant sprayed layer on at least its sliding surface. The sprayed layer consists of a ferrous alloy containing more than 2 percent but less than the stoichiometric amount based on FeS2 of S, or 20 95 wt. percent of the ferrous alloy and 80 - 5 wt. percent of at least one ingredient selected from the group consisting of W, Mo, Ni-Cr alloy, Ni-Al alloy, and mixtures thereof.

Unite States Nakamura atent 1 [451 ec. to, 1974 1 SLIDING MEMBER [75] Inventor: Yoshikatsu Nakamnra, Yokohama,

Japan [73] Assignee: Nippon Piston Ring Co., Ltd.,

Tokyo, Japan [22] Filed: Dec. 4, 1972 [21] Appl. No.: 311,619

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 2,233,304 2/1941 Bleakley 117/105 2,622,993 12/1952 McCullough et a]. 308/241 2,901,380 8/1959 Crump 308/241 3,342,626 9/1967 Batchelor et a1. 117/131 3,669,719 6/1972 Doede et a1. 117/93.1 PF 3,705,818 12/1972 Grosseau 117/105 Primary Examiner-William D. Martin Assislant ExaminerJohn H. Newsome Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A sliding member having a scuff resistant and abrasion resistant sprayed layer on at least its sliding surface. The sprayed layer consists of a ferrous alloy containing more than 2 percent but less than the stoichiometric amount based on FeS of S, or 20 95 wt. percent of the ferrous alloy and 80 5 wt. percent of at least one ingredient selected from the group consisting of W, Mo, Ni-Cr alloy, Ni-Al alloy, and mixtures thereof.

2 Claims, 1 Drawing Figure SLIDING MEMBER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a sliding member, for example, a piston ring or cylinder liner of an internal combustion engine. More particularly, the present invention provides a sliding member having excellent scuff resistant and abrasion resistant sprayed layer on at least its sliding surface.

2. Description of the Prior Art Heretofore, a surface treatment has been applied to the sliding surface of sliding members such as a piston ring, a cylinder liner, etc. in order to impart abrasion resistance thereto.

One of the conventional surface-treating processes is the sulfurizing process. The effective depth of the sulfurized layer obtained by the liquid, solid or gas sulfurizing process is generally about 0.l mm or less; especially the sulfurized layer formed on the cast iron base body is extremely thin so that it is not durable for a long period of use under the severe normal operating conditions. On the contrary, the base body of the sliding member must be made from iron or steel in order to form the FeS layer thereon. On the other hand, the sulfurizing process requires the use of poisonous chemicals, such as NaCN, which is very injurious to health. In addition, since the base body must be treated at a high temperature such as 400 600C, this sulfurizing process has adverse effects upon the properties of the sliding member.

SUMMARY OF THE INVENTION The present invention overcomes the abovedescribed defect of the conventional sulfurizing process and provides a sliding member having a sprayed layer on at least its sliding surface.

According to the present invention, the sprayed layer comprises a ferrous alloy containing 2 53.5 wt. percent more than 2 percent but less than the stoichiometric amount based on FeS of S, or 20 95 wt. percent of the ferrous alloy and 80 5 wt. percent of at least one ingredient selected from the group consisting of W, Mo, Ni-Cr alloy, Ni-Al alloy and mixtures thereof, and is superior to the FeS layer obtained by the conventional sulfurizing process in scuff resistance and abrasion resistance.

BRIEF EXPLANATION OF THE ACCOMPANYING DRAWING The FIGURE shows the abrasion resistance of several piston ring specimens in an actual engine test, wherein specimen No. l is a conventional piston ring having a sprayed Mo layer, specimen No. 2 is the piston ring of this invention as described in Example 1 below.

DETAILEDEXPLANATION OF THIS INVENTION One embodiment of the present invention is a sliding member having a scuff resistant and abrasion resistant sprayed layer on at least its sliding surface which is formed by spraying a ferrous alloy containing 2 53.5 wt percent, or more than 2 percent by weight but less than the stoichiometric amount based on FeS of S, of sulfur on a surface of a base body of the sliding member. The spraying treatment as described above ineludes not only the plasma-spraying treatment but also the gas-spraying treatment.

In the spraying treatment of the present invention, since fine particles of a ferrous alloy containing sulfur are sprayed extremely strongly, the resultant sprayed layer laminated on the surface of the base body is strongly adhered to the surface of the base body and has excellent abrasion resistance properties, and in particular, the layer is formed as a porous structure having a small coefficient of friction. Therefore, the sliding member laminated with such a sprayed porous layer on its sliding surface is impregnated with lubricating oil when it is actually used, so that it has sufficient oil retention properties. Accordingly, since the sliding property of the sliding surface can be kept in a favorable and stable state even under severe operating conditions and the abrasion of the sliding surface is remarkably reduced, the sliding member of the present invention can be used for long periods of time under such conditions which cause scuffing on the sliding surface.

The hardness of the sprayed layer of the present invention is usually about 500 600 HV (30), however, if a higher hardness than the usual value is desired, a small amount of a metal oxide such as A1 0 or the like or a metal carbide such as WC or the like may be added to the ferrous alloy containing sulfur.

Through many empirical tests, if the sulfur content in the sprayed layer is not more than 2 wt. percent the scuff resistance of the sliding member does not reach the desired level. On the other hand, if the sulfur content exceeds 53.5 wt. percent (the theoretical sulfur content in FeS is 53.5 wt. percent), the hardness of the sprayed layer is undesirably decreased to cause a reduction in the abrasion resistance. Accordingly, the sulfur content in the sprayed layer must be restricted in a range of 2 to 53.5 wt. percent.

Now more specific embodiments of this invention will be explained with reference to the accompanied drawing and some examples, without intending to limit the scope of the invention.

EXAMPLE I Spraying Gun: Metco type 3M plasma-spraying gun Amount of N Gas Flow: I00 ftlhr. Pressure of N Gas: 50 lb/in. Amount of H Gas Flow: 10 ft lhr. Pressure of H Gas: 50 lb/in. Electric current: 300 A Spraying Distance: 4 in.

EXAMPLE 2 A powder of a mixture composed of 0.2 percent of TC (total carbon), 0.4 percent of Si, 0.5 percent of Mn, .10 percent of S, by weight, and the balance Fe was plasma-sprayed on a peripheral surface of a cast iron piston ring having the same composition as that described in Example 1 to form a porous sprayed layer having a thickness of 0.3 mm. The HV (30) hardness of the sprayed layer was 550. The spraying gunand the spraying conditions used were the same as that described in Example 1.

The piston ring specimens obtained in the Example 1, and another piston ring specimen obtained according to a process described in U.S. Pat. No. 3,133,739 were subjected to the actual engine testing to evaluate their abrasion resistance.

The process described in U.S. Pat. No. 3,133,739 has as an object the improvement in the scuff resistance of the sliding member and is characterized by providing a plurality of grooves on the outer periphery of the piston ring and spraying metallic Mo on these grooves.

The results of the abrasion resistance tests are shown in the FIGURE, wherein specimen No. 1 is the piston ring having a sprayed layer of 100 percent Mo formed by the process according to U.S. Pat. No. 3,133,739, and specimen No. 2 is the piston ring obtained by the process of Example 1 of this invention.

The engine testing was carried out under the following conditions:

Engine Used:

Running Conditions:

It will be apparent from the results shown in the FIG- URE that specimen No. 1 shows an abrasion about of 0.6 14, whereas specimen No. 2 shows an abrasion amount of only about of one-third of that of specimen No. 1'. This means that the abrasion resistance and scuff and resistance of the piston ring of this invention is far better than that of the conventional piston ring.

In addition, the sulfur containing ferrous alloy is lowpriced and is easily obtained in comparison with metallic Mo, so that the material cost of this invention is about one-thirtieth of that of the Mo sprayed piston ring. Furthermore, as shown in the FIGURE, the abrasion amount of the piston ring of this invention is about one-thirtieth of that of the Mo sprayed piston ring, in the words, the abrasion resistance of the piston ring of this invention is three times larger that of the Mo sprayed piston ring.

Although the above refers exclusively to piston rings, the same resluts will be obtained on other sliding members.

According to another embodiment of the present invention,a sprayed layer of 20 95 wt. percent of a ferrous alloy containing 2 53.5 wt. percent of sulfur and 80 5 wt. percent of at least one ingredient selected from the group consisting of W, Mo, Ni Cr alloy, Ni A1 alloy, and mixtures thereof is laminated on the surface of the base body of the sliding member.

As a result of many empirical tests, if the content of the ingredient from said group in the sprayed layer is less than 5 wt. percent, the layer tends to form microscopic cracks and tends to wear out. In addition, the sliding member cannot perform a buffer action. On the other hand, if the ingredients content'exceeds 80 wt.

I sulfur in the above-described Examples 1 and 2 tends to form cracks thereat if the layer thickness exceeds about 0.2 mm, however, with a sprayed layer containing such metallic ingredients as W, Mo, N-Cr alloy and Ni-Al alloy in addition to a ferrous alloy containing sulfur the occurrence of cracks-can be prevented. The reason for the crack formation is believed to be the contacting on cooling of the fine sulfur containing alloy particles a high temperature formed during the spraying operation contract; as the plasma-sprayed particles are heated at extremely high temperature, cracks are easily formed.

On the other hand, the powder mixture composed of a ferrous alloy containing sulfur and at least one metallic ingredient selected from a group consisting of W, Mo, Ni-Cr, Ni-Al, and mixtures thereof can be sprayed into a thicker layer of greater than a thickness of about 0.2 mm without crack formation. Therefore the toughness of the layer is improved to satisfy the abrasion resistance.

EXAMPLE 3 A powder of a mixture composed of wt. percent of FeS and 10 wt. percent of W was plasma-sprayed on a surface of a base body of a piston ring for use in a marine internal combustion engine to form a sprayed layer having a thickness of 0.5 mm.

This sprayed layer showed a HV (30) hardness of 500 and no crack formation. The abrasion resistance and scuff resistance were also excellent and comparable with that of the sprayed layer as described in Examples l and 2.

As described above, the present invention provides a sliding member having excellent abrasion resistance and scuff resistance and a crackless sprayed layer on at least its sliding surface.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that the numerous modifications may be made by those skilled in the art without actually departing from the scope of the present invention.

Therefore, the appended claims are intended to cover all such equivalent variations as coming within the true spirit and scope of the present invention.

What is claimed is:

l. A sliding member comprising a scuff resistant and abrasion resistant sprayed layer composed of a ferrous alloy containing more than two per cent by weight but less than the stoichiometric amount based on FeS of sulfur laminated on at least its sliding surface.

2. A sliding member as claimed in claim 1, wherein said sprayed layer is composed of 20 wt. percent of a ferrous alloy containing 2 53.5 wt. percent of sulfur and 80 5 wt. percent of at least one ingredient selected from the group consisting of W, Mo, Ni-Cr alloy,

Ni-Al alloy, and mixtures thereof. 

1. A SLIDING MEMBER COMPRISING A SCUFF RESISTANT AND ABRASION RESISTANT SPRAYED LAYER COMPOSED OF A FERROUS ALLOY CONTAINING MORE THAN TWO PER CENT BY WEIGHT BUT LESS THAN THE STOICHIOMETRIC AMOUNT BASED ON FES2 OF SULFUR LAMINATED ON AT LEAST ITS SLIDING SURFACE.
 2. A sliding member as claimed in claim 1, wherein said sprayed layer is composed of 20 - 95 wt. percent of a ferrous alloy containing 2 - 53.5 wt. percent of sulfur and 80 - 5 wt. percent of at least one ingredient selected from the group consisting of W, Mo, Ni-Cr alloy, Ni-Al alloy, and mixtures thereof. 